TheWestpfel, C.Ogrodniczak, P.White, M. T. realisation of turbomachinery suitable for two-phase expansion in organic Rankine cycle (ORC) systems could unlock significant performance benefits. Several recent studies have explored two-phase turbomachinery flows using numerical simulations, however further development is hindered by a lack of any experimental data. This paper outlines a proposed two-phase blowdown facility for studying the high-speed two-phase expansion of molecularly complex organic fluids in stationary components. An overview of the test rig is presented, before a summary of the sizing and selection of key components, such as the working fluid, tanks, pump and heater is presented. A lumped-mass transient blowdown model is used to predict the conditions within the test rig during a representative blowdown run. Finally, steady-state non-equilibrium simulations are used to examine the expected test conditions.